posted by Megan .
Solve the equation on the interval [0,2pi).
Megan, look at how your post came out.
what is *2/2 supposed to be?
I have a feeling you mean √2/2
If so, then
since the cosine is positive in quadrants I and IV
2x = 45º or 2x = 315º
then x = 22.5º or x = 157.5º
but we know that the period of cos(2x) is 180º, so by adding 180 to each of our answers we get the other solutions in the given domain, or
x = 202.5º
x = 337.5º
just noticed that you probably wanted the solutions in radians, that would be
pi/8, 7pi/8, 9pi/8, and 15pi/8